JP2013107203A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of further surely detecting a short supply of slurry.SOLUTION: The polishing device 1 is equipped with a holding mechanism 10 for holding a wafer W and a polishing pad 21 for polishing the wafer W held by the holding mechanism 10. This polishing device is configured to polish the wafer W by moving relatively while making the polishing pad 21 contact with a surface to be polished Wa of the wafer W held by the holding mechanism 10, and includes: a slurry supply mechanism 30 for supplying slurry 31 to a contact part between the surface to be polished Wa and the polishing pad 21; a light source 41 for irradiating a probe light to the surface to be polished Wa; a light detector 43 for detecting a reflected light from the surface to be polished Wa to which the probe light has been irradiated; and a control device 50 for detecting an endpoint of polishing based on the information of reflected light detected by the light detector 43 and determining the supply condition of the slurry 31 based on the information of the reflected light.

Description

  The present invention relates to a polishing apparatus for polishing an object to be polished such as a semiconductor wafer.

  A CMP apparatus is exemplified as a polishing apparatus for polishing the surface of a semiconductor wafer. The CMP apparatus is widely used as a polishing apparatus that polishes the surface of a wafer with high precision by chemical mechanical polishing (CMP). In such a polishing apparatus, the wafer held by the chuck and the polishing pad attached to the polishing head are relatively rotated and pressed, and a slurry (Slurry) corresponding to the polishing content is brought into contact with the wafer and the polishing pad. Is supplied to cause a chemical and mechanical polishing action to polish the wafer surface flatly.

  During the polishing process, end point detection is performed to detect the polishing end point by measuring the polishing state in-situ. As a conventional end point detection method, a method for optically measuring the surface state of a wafer and performing end point detection is known. In this method, the surface to be polished of the wafer is irradiated with the probe light, the reflected light from the wafer irradiated with the probe light is detected, and the end point is detected based on the intensity change and the spectrum distribution. (For example, see Patent Document 1). When performing end point detection in this way, for example, as shown in FIG. 4, after the disturbance immediately after the start of slurry supply has subsided, the amount of reflected light (light intensity) is sampled, and the amount of light is adjusted so that the detected amount of light becomes the appropriate amount of light. Further, the end point determination was started after the flow of the slurry was settled and the detected light quantity was stabilized.

JP 2006-032764 A

  However, in the above polishing apparatus, the flow rate of the slurry was monitored using a flow meter, but the slurry leaked out due to a pipe crack or the like in the downstream portion of the flow meter, and the wafer and the polishing pad If sufficient slurry is not supplied to the abutting portion, the flow meter cannot detect the insufficient supply of the slurry, and there is a possibility that the polishing process may be performed in a state where the supply of the slurry is insufficient.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a polishing apparatus capable of more reliably detecting an insufficient supply of a polishing liquid (slurry).

  In order to achieve such an object, a polishing apparatus according to the present invention includes a holding mechanism that holds an object to be polished, and a polishing member that polishes the object to be polished held by the holding mechanism. In the polishing apparatus configured to perform polishing processing of the object to be polished by moving the polishing member in contact with the surface to be polished of the object to be held, the polishing surface and the polishing member A polishing liquid supply mechanism that supplies a polishing liquid to a contact portion with the light source, an illumination unit that irradiates the surface to be polished with probe light, and light that detects reflected light from the surface to be polished irradiated with the probe light A detection unit; an end point detection unit that detects an end point of the polishing process based on information of the reflected light detected by the light detection unit; and the information based on information of the reflected light detected by the light detection unit. The supply state of the polishing liquid to the contact part Constructed and a supply determination section for constant.

  According to the present invention, it is possible to more reliably detect an insufficient supply of the polishing liquid.

1 is a schematic view of a polishing apparatus according to the present invention. It is an enlarged view which shows the outline of the lower end part vicinity in an EPD part. It is a figure which shows the time change of the reflected light amount (light intensity) with respect to probe light. It is a figure which shows the time change of the reflected light amount (light intensity) with respect to the conventional probe light.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. A schematic configuration of a polishing apparatus 1 to which the present invention is applied is shown in FIG. The polishing apparatus 1 includes a holding mechanism 10 that rotatably holds a semiconductor wafer W on the upper surface side, a polishing head 20 that is provided above the holding mechanism 10 and is mounted with a polishing pad 21 on the lower surface side, and a polishing pad. The slurry supply mechanism 30 that supplies the slurry (polishing liquid) 31 from the central portion of 21, the EPD unit 40 that detects the end point, and the controller 50 that controls these operations are mainly configured.

  The holding mechanism 10 includes a disc-shaped chuck 11 and a spindle 12 that supports the chuck 11 and extends vertically downward. A rotation driving mechanism (not shown) rotates a rotation center axis O1 orthogonal to the upper surface of the chuck 11. The chuck 11 is driven to rotate in the horizontal plane at the center. The chuck 11 holds the wafer W by suction. The chuck 11 is provided with a vacuum chuck structure that vacuum-sucks the lower surface of the wafer W so that the wafer W can be attached and detached. The surface to be polished (that is, the surface to be polished) of the wafer W attracted and held by the chuck 11. Wa) is held in an upward horizontal posture.

  The polishing head 20 includes a head member 22 to which a polishing pad 21 is attached on the lower surface, and a spindle 23 that supports the head member 22 and extends vertically upward, and rotates perpendicularly to the lower surface of the head member 22 by a rotation drive mechanism (not shown). The polishing pad 21 is rotationally driven in the horizontal plane around the central axis O2. The polishing pad 21 is formed in an annular shape whose outer diameter is smaller than the outer diameter of the wafer W to be polished. For example, the polishing pad 21 is formed using a rigid polyurethane sheet having an independent foam structure, and the lower surface of the head member 22. The polished surface is held in a downward horizontal posture. The polishing head 20 is configured to be horizontally swingable and vertically movable with respect to the chuck 11 using a head moving mechanism (not shown).

  The slurry supply mechanism 30 supplies the slurry 31 to the contact portion between the polishing pad 21 and the wafer W from the holes 21a and 22a formed through the pipe 33 in the central portion of the polishing pad 21 and the head member 22 vertically. Supply. The pipe 33 is provided with a flow meter 34 for measuring the flow rate of the slurry 31 flowing through the pipe 33, and the measurement signal is output to the control device 50.

  The EPD unit 40 includes a light source 41 such as a xenon lamp or an LED lamp, a beam splitter 42, a photodetector 43, a lens optical system (not shown), and the like. Since the EPD unit 40 is disposed so as to be opposed to the upper side of the wafer W, the EPD unit 40 is accommodated in the cover 45 in order to protect the device from the slurry scattered during the polishing process. Further, the EPD unit 40 accommodated in the cover 45 is retracted from the measurement position located above the wafer W (chuck 11) and from above the wafer W (chuck 11) by using an EPD swing mechanism (not shown). It is configured to be able to swing back and forth between the retracted position.

  As shown in FIG. 2, the objective lens 44 constituting the lens optical system is attached to the lower part of the lens barrel portion 46 formed to extend below the cover 45. A groove portion 47 is formed in the attachment portion of the objective lens 44 at 46 to communicate the inside and outside of the cover 45 (lens barrel portion 46). Then, by sending air from the inside of the cover 45 into the lens barrel portion 46 by an air supply device (not shown), an air flow F is generated from the groove portion 47 of the lens barrel portion 46 toward the outside downward. The thin film portion 32 can be formed on a part of the slurry 31 supplied onto the polishing surface Wa of the wafer W by colliding with the slurry 31 positioned below the lens barrel portion 46 (that is, the EPD portion 40). It can be done. Thereby, since the slurry 31 can be thinned at the location where the end point is detected, the attenuation of the probe light and the reflected light is reduced, so that a decrease in the amount of light detected by the photodetector 43 can be suppressed.

  1 is based on a control program preset and stored in the polishing apparatus 1 and a processing program read in accordance with the object to be polished, the holding mechanism 10, the polishing head 20, and the slurry supply mechanism 30. And the operation of the EPD unit 40 and the like are controlled.

  In the polishing apparatus 1 configured as described above, in order to polish the wafer W, the chuck 11 and the head member 22 are rotated in the same direction or the opposite direction, respectively, and the center of the polishing pad 21 ( While supplying the slurry 31 from the hole 21a), the polishing head 20 is lowered to bring the polishing pad 21 into contact with the surface Wa of the wafer W. In this state, the polishing head 20 is moved to the central portion and the outer peripheral portion of the wafer W. Oscillate back and forth in the radial direction (horizontal). As a result, the surface Wa of the wafer W is subjected to the mechanical and chemical polishing action of the slurry 31 interposed between the polishing pad 21 and the wafer W is polished flat.

  At the time of polishing, end point detection is performed using the EPD unit 40. At this time, the probe light emitted from the light source 41 of the EPD unit 40 is transmitted through the beam splitter 42 to the polished surface Wa of the wafer W. The reflected light that has been irradiated and reflected by the surface Wa of the wafer W is reflected by the beam splitter 42 and received by the photodetector 43. Then, the light detection signal detected by the light detector 43 is output to the control device 50, and the control device 50 performs polishing processing based on the change in the amount of light (light intensity) of the reflected light detected by the light detector 43. Determine the end point.

  Here, the procedure of end point detection using the EPD unit 40 will be described with reference to FIG. First, after the wafer W is transferred onto the chuck 11 by a transfer device (not shown) and before the polishing process is started, the control device 50 uses the EPD swing mechanism (not shown) to move the EPD unit 40 from the retracted position to the wafer. Move to the measurement position above W. At this time, the air flow F is generated below the lens barrel portion 46 by sending air from the inside of the cover 45 into the lens barrel portion 46 by an air supply device (not shown) before the start of the polishing process (see FIG. 2). reference). Before starting the polishing process, a relatively weak air flow F is generated to prevent water droplets from adhering to the objective lens 44 and the like, and after starting the polishing process, the slurry 31 is made thin. It is preferable to generate an air flow F having a relatively strong flow.

  Next, the control device 50 operates the slurry supply mechanism 30 to start supplying the slurry 31 and starts polishing, and at the same time, irradiates probe light from the light source 41 of the EPD unit 40 to detect light. Measurement of reflected light by the instrument 43 (that is, measurement by the EPD unit 40) is started. Thereafter, the light detection signal detected by the light detector 43 is output to the control device 50, and the detected light amount (light intensity) of the reflected light is recorded in a memory (not shown). Note that such measurement by the EPD unit 40 is preferably started before the supply of the slurry 31 is started.

  After the supply of the slurry 31 is started, the slurry 31 that has flowed through the pipe 33 from the slurry supply mechanism 30 is discharged from the hole 21a of the polishing pad 21 and reaches the surface to be polished Wa of the wafer W. Since the detector 43 detects the reflected light from the wafer W in a state where the slurry 31 is not supplied, the light amount (light intensity) of the reflected light is almost maximized. Then, when the slurry arrival time t1 (for example, about 2 seconds from the start of the slurry supply) when the slurry 31 reaches the surface Wa of the wafer W is reached, the surface 31 of the wafer W is covered with the slurry 31 and light. The amount of reflected light detected by the detector 43 is drastically reduced.

  At this time, the controller 50 records in the memory the time from when the supply of the slurry 31 starts until the amount of reflected light decreases drastically, that is, the slurry arrival time t1, and when the slurry arrival time t1 is longer than a predetermined set time, It is determined that the time until 31 reaches is long, and control is performed to stop the polishing process. At this time, the control device 50 records the amount of decrease when the amount of reflected light is drastically reduced in the memory. It is determined that the slurry 31 is thin or has not spread to the outer peripheral side of the wafer W, and control is performed to stop the polishing process.

  When the disturbance immediately after the start of slurry supply subsides (at time t2), the control device 50 samples the reflected light amount (light intensity) detected by the photodetector 43 and adjusts the light amount so that the detected light amount becomes an appropriate light amount. I do. Then, after adjusting the light amount, the control device 50 starts the end point determination after the slurry flow has settled and the detected light amount has stabilized (after time t3). The time t2 for starting light amount adjustment (for example, about 5 seconds from the start of slurry supply) and the time t3 for starting end point determination (for example, about 10 seconds from the start of slurry supply) are set empirically.

  After the start of the end point determination, the control device 50 determines the end point of the polishing process based on the change in the amount of light (light intensity) of the reflected light detected by the photodetector 43. For example, in the process of flattening a metal film embedded in a damascene process by metal CMP, polishing is performed when the amount of reflected light (reflectance) detected by the photodetector 43 decreases to a predetermined value. It determines with it being the end point of a process, and performs control which complete | finishes the said polishing process. Further, for example, in the case of a CMP process (a shallow trench isolation (STI) process or an interlayer insulating film (ILD) process) for polishing a silicon oxide film, the amount of reflected light (reflectance) detected by the photodetector 43 When the maximum point appears in the change a predetermined number of times, it is determined that it is the end point of the polishing process, and control to end the polishing process is performed.

  In addition, after starting the end point determination, the control device 50 has an insufficient supply amount of the slurry 31 when the reflected light amount (light intensity) detected by the photodetector 43 exceeds a predetermined threshold value (reference light amount). And control to stop the polishing process. From the start of supply of the slurry 31 by the slurry supply mechanism 30, the flow meter 34 measures the flow rate of the slurry 31 flowing through the pipe 33 and outputs the measurement signal to the control device 50. Then, the control device 50 determines that the supply amount of the slurry 31 is abnormal when the flow rate of the slurry 31 measured by the flow meter 34 is significantly larger or smaller than the flow rate instructed to the slurry supply mechanism 30. And control to stop the polishing process. As a result, the supply amount of the slurry 31 is double checked using the flow meter 34 and the EPD unit 40.

  As described above, according to the polishing apparatus 1 of the present embodiment, the control device 50 is supplied to the contact portion between the wafer W and the polishing pad 21 based on the information of the reflected light detected by the photodetector 43. In order to determine the supply state of the slurry 31, the slurry leaks due to a pipe crack or the like at a portion downstream of the flow meter 34, and sufficient slurry is not supplied to the contact portion between the wafer W and the polishing pad 21. However, since the supply shortage of the slurry can be detected using the photodetector 43 of the EPD unit 40, the supply shortage of the slurry can be detected more reliably.

  At this time, if the reflected light amount (light intensity) detected by the photodetector 43 exceeds a predetermined threshold value (reference light amount), it can be determined that the supply amount of the slurry 31 is insufficient. Without considering these parameters, it is possible to easily detect the shortage of slurry supply.

  In the above-described embodiment, as shown in FIG. 1, the holding mechanism 10 that holds the wafer W in an upward horizontal posture, and the polishing pad 21 that faces the lower side of the holding mechanism 10 and faces downward is provided on the lower surface side. However, the present invention is not limited to this, and the present invention is not limited to this, and the present invention is directed to a holding mechanism that holds the wafer in a downward horizontal posture and a lower portion of the holding mechanism. And a polishing device (so-called conventional type) having a polishing member on which the polishing pad is mounted upward on the upper surface side.

  Further, in the above-described embodiment, the object to be polished is not limited to the wafer W, and the present invention can be applied even in the case of a glass substrate, for example.

W Wafer (object to be polished) Wa Surface to be polished 1 Polishing device 10 Holding mechanism 20 Polishing head 21 Polishing pad (polishing member)
30 Slurry supply mechanism (polishing liquid supply mechanism)
31 Slurry (polishing liquid)
40 EPD part 41 Light source (illumination part) 43 Light detector (light detection part)
50 Control device (end point detection unit and supply determination unit)

Claims (2)

A holding mechanism for holding an object to be polished; and a polishing member for polishing the object to be polished held by the holding mechanism; and the polishing member is disposed on a surface to be polished of the object to be polished held by the holding mechanism. In a polishing apparatus configured to perform a polishing process of the object to be polished by moving relatively while abutting,
A polishing liquid supply mechanism for supplying a polishing liquid to a contact portion between the surface to be polished and the polishing member;
An illumination unit for irradiating the polished surface with probe light;
A light detection unit for detecting reflected light from the polished surface irradiated with the probe light;
An end point detection unit that detects an end point of the polishing process based on information of the reflected light detected by the light detection unit;
A polishing apparatus comprising: a supply determination unit that determines a supply state of the polishing liquid to the contact portion based on information of the reflected light detected by the light detection unit.   The supply determination unit determines that the supply amount of the polishing liquid to the contact portion is insufficient when the amount of the reflected light detected by the light detection unit exceeds a predetermined reference light amount. The polishing apparatus according to claim 1, wherein the polishing apparatus is characterized.

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